The Sustainability Engineering Process is implemented by GSEP and GSSE
and both processes supply the defined outcomes. GSEP identifies factors that affect
sustainability explicitly within requirements engineering, whereas GSSE references
a schematic Life Cycle model of software products that has the sole purpose
of collating exemplary effects and impacts on sustainable development with life
cycle phases known from Life Cycle Analysis (manufacturing, distribution, usage,
end of life). Both processes perform sustainability analysis to determine the impact
of the sustainability factors. GSEP has the Requirements and the Green Analysis
phase and GSSE has the Reviews and Previews as well as Process Assessment.
GSEP explicitly defines sustainability objectives in Requirements, whereas GSSE
mentions sustainability objectives implicitly together with the role of the Development
Team. The team is responsible for the non-functional requirements [13]
and is therefore responsible to drive the Reviews and Previews. Exactly where the
sustainability objectives as non-functional requirements are defined is left by
GSSE to the specific implementation of the target process. GSEP and GSSE refer
to principles and guidelines that are helpful to find adequate techniques and
methods appropriate to accomplishing the sustainability objectives. Regarding the
techniques and methods for sustainability, GSEP defines a large group of metrics
and tools in its second level. GSSE mentions a carbon footprint calculation and
especially methods and metrics to measure and assess the energy efficiency of
software. The reference process requires an analysis of the sustainability of change
requests, which is not specifically implemented by GSEP or GSSE. However, both
processes claim to be agile and thus should welcome changes. GSEP may possibly
analyze change requests in Requirements or the Green Analysis; GSSE may
handle change requests in Reviews and Previews.